Abstract: ObjectiveEffects of polycyclic aromatic hydrocarbons(PAHs) stress on Brassica parachinensis Bailey quality and its detoxification system were discussed to study the stress mechanism of PAHs on B. parachinensis Bailey and provide reference basis to ensure B. parachinensis Bailey quality.MethodUsing 16 kinds of PAHs to stress B. parachinen-sis Bailey, variations of single plant fresh weight, chlorophyll, soluble sugar, soluble protein, vitamin C(Vc), crude fiber and superoxide dismutase(SOD), catalase(CAT), ascorbate peroxidase(APX), peroxidase(POD) and polyphenol oxidase (PPO) activities were tested. After that, the quality indicators and related enzymes activities and their relationships with PAHs were analyzed. Result900.0 μg/L PAHs stress decreased single plant fresh weight by 12.65%. 300.0-900.0 μg/L PAHs lowered Vc and chlorophyll contents, but increased crude fiber content in B. parachinensis Bailey. In this way, PAHs changed the color and made the taste worse, but it could increase the soluble protein content and start the immune sys-tem of B. parachinensis Bailey. Low concentration(300.0 μg/L) of PAHs could cause vegetable soluble sugar content lower and the taste worse. PAHs stress made the related enzymes activities up- or down-regulated to remove PAHs stress. SOD activity decreased;CAT activity went through a down-up variation, but the variation range was smaller than that of control(CK); POD activity decreased as stress time extended, which indicated that CAT and POD shared partial detoxifica-tion function. 600.0 μg/L PAHs could promote APX activity; PPO activity increased first and then declined, which was be-neficial for self-healing process. ConclusionUnder the stress of PAHs, the quality of B. parachinensis Bailey is worse. Low concentration(300.0 μg/L) of PAHs stress improves CAT and POD activities. Medium concentration (600.0 μg/L) of PAHs stress is beneficial for improving SOD activity to lower PAHs accumulation in B. parachinensis Bailey.